I don't have one, but I do know a lot about the standard iTunes movie format. That being said, since most of iTunes' videos on its store use the H.264, it only seems fit that the video recordings use the same exact codec with the MP4 or M4V container.

Also, I just checked their website and looked at the specs, it says the following.

quote

H.264 VGA video, 640 x 480 pixels, up to 30 frames per second with AAC audio

With that in mind, if you preview a music video, or a get one of the free music videos a week, the quality should be about the same as that.